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Biomedical subjects

J Lieberman

Publications and source records attributed to J Lieberman.

At least 55 records · Page 3Linked to original sources
PubMed1999

Mitochondria-dependent and -independent regulation of Granzyme B-induced apoptosis.

Granzyme B (GraB) is required for the efficient activation of apoptosis by cytotoxic T lymphocytes and natural killer cells. We find that GraB and perforin induce severe mitochondrial perturbation as evidenced by the release of cytochrome c into the cytosol and suppression of transmembrane potential (Deltapsi). The earliest mitochondrial event was the release of cytochrome c, which occurred at the same time as caspase 3 processing and consistently before the activation of apoptosis. Granzyme K/perforin or perforin treatment, both of which kill target cells efficiently but are poor activators of apoptosis in short-term assays, did not induce rapid cytochrome c release. However, they suppressed Deltapsi and increased reactive oxygen species generation, indicating that mitochondrial dysfunction is also associated with this nonapoptotic cell death. Pretreatment with peptide caspase inhibitors zVAD-FMK or YVAD-CHO prevented GraB apoptosis and cytochrome c release, whereas DEVD-CHO blocked apoptosis but did not prevent cytochrome c release, indicating that caspases act both up- and downstream of mitochondria. Of additional interest, Deltapsi suppression mediated by GraK or GraB and perforin was not affected by zVAD-FMK and thus was caspase independent. Overexpression of Bcl-2 and Bcl-XL suppressed caspase activation, mitochondrial cytochrome c release, Deltapsi suppression, and apoptosis and cell death induced by GraB, GraK, or perforin. In an in vitro cell free system, GraB activates nuclear apoptosis in S-100 cytosol at high doses, however the addition of mitochondria amplified GraB activity over 15-fold. GraB- induced caspase 3 processing to p17 in S-100 cytosol was increased only threefold in the presence of mitochondria, suggesting that another caspase(s) participates in the mitochondrial amplification of GraB apoptosis. We conclude that GraB-induced apoptosis is highly amplified by mitochondria in a caspase-dependent manner but that GraB can also initiate caspase 3 processing and apoptosis in the absence of mitochondria.

Animals↗
PubMed1999

Granzyme A loading induces rapid cytolysis and a novel form of DNA damage independently of caspase activation.

Cytotoxic lymphocytes trigger apoptosis by releasing perforin and granzymes (Grn). GrnB activates the caspase apoptotic pathway, but little is known about GrnA-induced cell death. Perforin was used to load recombinant GrnA and GrnB and enzymatically inactive variants into target cells. GrnA induces single-strand DNA breaks that can be labeled with Klenow polymerase and visualized on alkaline gels. GrnA-induced DNA damage but not cytolysis requires GrnA proteolysis. GrnA-induced membrane perturbation, nuclear condensation, and DNA damage are unimpaired by caspase blockade. GrnA fails to induce cleavage of caspase-3, lamin B, rho-GTPase, or PARP. GrnA-induced cytotoxicity and cleavage of PHAP II, a previously identified GrnA substrate, are unimpaired in Jurkat cells that overexpress bcl-2. Therefore, GrnA activates a novel apoptotic pathway.

Animals↗
PubMed1999

Analysis of genome-wide CAG/CTG repeats, and at SEF2-1B and ERDA1 in schizophrenia and bipolar affective disorder.

A shift towards larger CAG/CTG triplet repeats and schizophrenia (SCZ) and bipolar affective disorder (BPAD) has been detected by several recent studies, using the Repeat Expansion Detection (RED) technique, however no specific loci have been shown to be responsible for this shift. Further analyses by our group of RED (CTG)10 ligation products amongst an extended sample of patients and comparison with controls matched for age, sex and ethnicity show no significant differences in distribution (P= 0.23, n=95; P=0.93, n=91, for SCZ and BPAD respectively). Alleles at two recently discovered unstable trinucleotide repeat loci at 18q21.1 (SEF2-1B) and 17q21.3 (ERDA1) have also been analysed in affecteds and matched controls. We observed no increase in frequency of larger alleles (>37 repeats) in affected individuals at SEF2-1B (BPAD: P=0.95, n= 100; SCZ: P=0.61, n=97) or at ERDA1 (BPAD: P= 0.4, n = 101; SCZ: P= 0.05, n = 151, with larger alleles more frequent in controls). Our findings suggest that larger CAG/CTG repeats at these loci are neither major contributory factors to the etiology of psychosis, nor in linkage disequilibrium with a gene that is. Furthermore, when the RED results were compared to allele sizes at SEF2-1B and ERDA1, it was observed that a majority of SCZ, BPAD and control individuals with large RED products had a large allele at either or both sites (78% for RED products > or =270 bp; 62% for RED products > or =180 bp).

Adult↗
PubMed1999

Treatment of human immunodeficiency virus infection with hydroxyurea, didanosine, and a protease inhibitor before seroconversion is associated with normalized immune parameters and limited viral reservoir.

Current treatments for human immunodeficiency virus (HIV) require uninterrupted drug administration because they are unable to reconstitute the immune response and do not affect the viral reservoir. Ten patients were treated during acute HIV infection before complete Western blot (WB) seroconversion with the combination of hydroxyurea, didanosine, and indinavir. This treatment was associated with the normalization of some immune parameters and functions. No loss of naive CD4 T lymphocytes was observed, and recovery of up to 35% of naive CD8 T lymphocytes occurred in several weeks. A vigorous HIV-specific T helper response (stimulation index >8) was observed in 7 of 8 patients treated before complete WB seroconversion but in only 1 of 5 controls treated after seroconversion. In addition, a limited latent viral reservoir (<0.02-0.5 infectious units/106 cells) was documented in quiescent peripheral blood lymphocytes after treatment initiated before complete WB seroconversion.

Anti-HIV Agents↗
PubMed1998

Effects of clozapine on auditory event-related potentials in schizophrenia.

BACKGROUND: Schizophrenia is associated with cognitive deficits that are an intrinsic component of the disorder. Clozapine is an atypical antipsychotic that is superior to typical agents in the treatment of positive symptoms. The degree to which clozapine ameliorates cognitive deficits, however, is still controversial. Mismatch negativity (MMN), N200 (N2), and P300 (P3) are cognitive event-related potentials (ERPs) that index preattentive (MMN) and attention-dependent information processing (N2, P3) and provide a measure of cognitive deficits associated with schizophrenia. In schizophrenic patients deficient generation of MMN, N2, and P3 has been observed, suggesting impairments of discrete stages of information processing. METHODS: This study investigates the effects of clozapine treatment on MMN, N2, and P3 generation. Patients were recruited from a haloperidol-controlled, double-blind treatment study of clozapine in chronic schizophrenia. ERPs were obtained at the beginning of the study and after 9 weeks (4 patients) and 16 weeks (13 patients) of treatment. RESULTS: Clozapine treatment was associated with a significant increase of P3 amplitude, which was not observed in the haloperidol group; however, clozapine treatment did not affect deficits in MMN and N2. CONCLUSIONS: These findings suggest that clozapine--in contrast to conventional antipsychotics--improves electrophysiological measures of attention-dependent information processing, but does not ameliorate preattentive deficits.

Adult↗
PubMed1998

Striatal enlargement in rats chronically treated with neuroleptic.

BACKGROUND: Striatal enlargement with chronic neuroleptic treatment in schizophrenic patients has been reported by several investigators. Longitudinal magnetic resonance imaging studies of patients suggest that changes in striatal volume may be caused by treatment with antipsychotic medication. METHODS: We have examined the effects of chronic neuroleptic treatment on postmortem striatal volume in the laboratory rat and have examined the relationship between striatal volume and vacuous chewing movements (VCMs). Autoradiographs of 50 rats treated with haloperidol (1.5 mg/kg/day) or drug free for varying durations of time (1-12 months) were utilized in this analysis. RESULTS: Chronic treatment with neuroleptics (1 month or greater) was associated with larger striatal volumes. The increase in striatal volume was present at 1 month of treatment and was sustained to 12 months of treatment. Rats that developed the high-VCM syndrome had larger striatal volumes than both drug-free and low-VCM rats, while low-VCM rats had larger striatal volumes than drug-free rats. CONCLUSIONS: These data suggest that chronic neuroleptic treatment is the cause of striatal enlargement in the laboratory rat, and that this enlargement is most prominent in rats that have the high-VCM syndrome.

Animals↗
PubMed1998

Effective lysis of HIV-1-infected primary CD4+ T cells by a cytotoxic T-lymphocyte clone directed against a novel A2-restricted reverse-transcriptase epitope.

Most HIV-specific cytotoxic T-lymphocyte (CTL) epitopes have been identified using peptide-pulsed and recombinant vaccinia virus-infected targets. These systems may not accurately reflect the ability of epitopes to be presented by HIV-infected T cells. Recent studies suggest, in fact, that some CTL epitopes are poorly presented on HIV-infected cells. In this study, we have identified a novel A2.1-restricted HIV reverse-transcriptase (RT) epitope and investigated the presentation of this epitope by HIV-infected primary CD4+ T cells and T-cell lines. A CD8+ CTL clone, isolated from a seropositive subject that recognized a novel A2-restricted epitope KYTAFTIPSI (aa 293-302) in RT, was used for these studies. Primary CD4+ T cells and the CD4+ T-cell line T1 were infected with virus from T1-nPLAP, a cell line stably transfected with HXB-nPLAP, a molecular construct of HIV linked to a placental alkaline phosphatase (PLAP) marker gene. A uniformly infected cell population, obtained by immunomagnetic selection for PLAP expression, was used as targets in CTL assays. HIV-infected T cells were lysed by CTL recognizing this RT epitope as effectively as peptide-pulsed targets. This suggests that some RT epitopes are good targets for CTL recognition.

Amino Acid Sequence↗
PubMed1998

A role for heat shock protein 27 in CTL-mediated cell death.

CTL exocytosis of granules containing perforin and granzyme proteases induces apoptotic cell death. Either granzyme A or B can act with perforin to trigger apoptosis. Granzyme B activates a ubiquitous apoptotic cascade induced by caspase cleavage, but the granzyme A pathway is largely unknown. Using affinity chromatography with recombinant mutant inactive granzyme A, we previously isolated two granzyme A-binding proteins, PHAP (putative HLA-associated protein) I and II. PHAP II, a substrate of granzyme A, is degraded within minutes of CTL attack. Two additional cytoplasmic proteins of 27 and 53 kDa bind strongly to the mutant granzyme A column, requiring 6 M urea to elute. Sequencing identified these as the monomer and dimer of hsp27, a small heat shock protein up-regulated by stress and cellular activation. Hsp27 coprecipitates with granzyme A from cytoplasmic lysates and is not a substrate of the enzyme. Hsp27 translocates to the detergent-insoluble fraction of target cells and relocalizes from diffuse cytoplasmic staining to long filamentous fibers, especially concentrated in a perinuclear region, within minutes of CTL attack. Hsp27 may participate in morphologic changes during granule-mediated lysis. Low or absent levels of hsp27 expression in T lymphocytes, even after heat shock, may play a role in CTL resistance to granule-mediated lysis.

Cell Death↗
PubMed1998

Expression and purification of enzymatically active recombinant granzyme B in a baculovirus system.

Granzyme B (GranB), a serine protease stored in the granules of cytotoxic T lymphocytes and natural killer cells, can initiate target cell apoptosis. To produce large amounts of purified active enzyme, recombinant murine granzyme B (rGranB) was expressed from baculovirus in insect cells. The expressed rGranB is secreted into the culture medium and can be readily purified to homogeneity by one-step affinity chromatography to yield 1.5 mg enzyme per liter insect cell medium. RGranB is recognized by a GranB-specific anti-peptide antibody and is active against synthetic substrate Boc-Ala-Ala-Asp-SBzl with kinetic constant (kcat/Km 45,000 M-1s-1) comparable to purified human GranB, RGranB processes the caspase pro-CPP32 into its enzymatically active form and induces DNA fragmentation in isolated nuclei in the presence of cytosolic factors. The ability to express enzymatically active rGranB using the baculovirus system will help elucidate the role of this granzyme in the immune response.

Animals↗
PubMed1998

Human cardiovascular and metabolic response to acute, severe isovolemic anemia.

CONTEXT: Although concern over the risks of red blood cell transfusion has resulted in several practice guidelines for transfusion, lack of data regarding the physiological effects of anemia in humans has caused uncertainty regarding the blood hemoglobin (Hb) concentration requiring treatment. OBJECTIVE: To test the hypothesis that acute isovolemic reduction of blood Hb concentration to 50 g/L in healthy resting humans would produce inadequate cardiovascular compensation and result in tissue hypoxia secondary to inadequate oxygen transport. DESIGN: Before and after interventional study. SETTING: Academic tertiary care medical center. PARTICIPANTS: Conscious healthy patients (n =11) prior to anesthesia and surgery and volunteers not undergoing surgery (n=21). INTERVENTIONS: Aliquots of blood (450-900 mL) were removed to reduce blood Hb concentration from 131 (2) g/L to 50 (1) g/L [mean (SE)]. Isovolemia was maintained with 5% human albumin and/or autologous plasma. Cardiovascular parameters, arterial and mixed venous oxygen content, oxyhemoglobin saturation, and arterial blood lactate were measured before and after removal of each aliquot of blood. Electrocardiogram and, in a subset, Holter monitor were monitored continuously. MAIN OUTCOME MEASURES: "Critical" oxygen delivery (TO2) as assessed by oxygen consumption (VO2), plasma lactate concentration, and ST changes on electrocardiogram. RESULTS: Acute, isovolemic reduction of Hb concentration decreased systemic vascular resistance and TO2 and increased heart rate, stroke volume, and cardiac index (each P<.001). We did not find evidence of inadequate oxygenation: VO2 increased slightly from a mean (SD) of 3.07 (0.44) mL of oxygen per kilogram per minute (mL O2 x kg(-1) x min[-1]) to 3.42 (0.54) mL O2 x kg(-1) x min(-1) (P<.001) and plasma lactate concentration did not change (0.81 [0.11] mmol/L to 0.62 [0.19] mmol/L; P=.09). Two subjects developed significant ST changes on Holter monitor: one apparently related to body position or activity, the other to an increase in heart rate (at an Hb concentration of 46-53 g/L); both occurred in young women and resolved without sequelae. CONCLUSIONS: Acute isovolemic reduction of blood Hb concentration to 50 g/L in conscious healthy resting humans does not produce evidence of inadequate systemic TO2, as assessed by lack of change of VO2 and plasma lactate concentration. Analysis of Holter readings suggests that at this Hb concentration in this resting healthy population, myocardial ischemia would occur infrequently.

Adult↗
PubMed1998

Circulating CD8 T lymphocytes in human immunodeficiency virus-infected individuals have impaired function and downmodulate CD3 zeta, the signaling chain of the T-cell receptor complex.

Although human immunodeficiency virus (HIV)-infected subjects without acquired immunodeficiency syndrome have a high frequency of HIV-specific CD8 T lymphocytes, freshly isolated lymphocytes frequently lack detectable HIV-specific cytotoxicity. However, this effector function becomes readily apparent after overnight culture. To investigate reasons for T-cell dysfunction, we analyzed T-cell expression of the cytolytic protease granzyme A and CD3 zeta, the signaling component of the T-cell receptor complex. An increased proportion of CD4 and CD8 T cells from HIV-infected donors contain granzyme A, consistent with the known increased frequency of activated T cells. In 28 HIV-infected donors with mild to advanced immunodeficiency, a substantial fraction of circulating T cells downmodulated CD3 zeta (fraction of T cells expressing CD3 zeta, 0.74 +/- 0.16 v 1.01 +/- 0.07 in healthy donors; P < .0000005). CD3 zeta expression is downregulated more severely in CD8 than CD4 T cells, decreases early in infection, and correlates with declining CD4 counts and disease stage. CD3 zeta expression increases over 6 to 16 hours of culture in an interleukin-2-dependent manner, coincident with restoration of viral-specific cytotoxicity. Impaired T-cell receptor signaling may help explain why HIV-specific cytotoxic T lymphocytes fail to control HIV replication.

CD3 Complex↗
PubMed1998

Emerging roles for novel antipsychotic medications in the treatment of schizophrenia.

Antipsychotic medications are the mainstay of treatment for schizophrenia. The recent advent of atypical antipsychotics has provided new clinical options and set higher expectations for the treatment of schizophrenia. It is not yet clear how each different drug will fit within the therapeutic armamentarium and this lack is most evident with considering patients with treatment refractory schizophrenia. On the other hand, the expectation of superior efficacy, more benign side effect profile and potential to impact the longitudinal course of schizophrenia provide a rationale for the use of novel antipsychotics as a first-line treatment of schizophrenia.

Antipsychotic Agents↗
PubMed1998

The dentition of Abraham's people. Why Abraham left Mesopotamia.

Ancient Mesopotamia (southern Iraq) in 2000 B.C. was the home of the biblical figure Abraham and his people. An analysis of skeletal material from cemeteries in the ancient cities of Ur (birthplace of Abraham) and Kish shows a homogeneous, short-lived population that suffered severe dental attrition (95 percent of inhabitants), periodontal disease (42 percent) and caries (two percent). Many oral congenital and neoplastic lesions were noted Skeletal (dental) evidence indicates the population suffered from extensive disease and nutritional deficiency. Of special note was a possible case of endodontic treatment. The people of Abraham had modern dentition but relatively poor dental health. It is probable that Abraham, if in truth he existed, left Mesopotamia because of the threat of famine, as evidenced by biblical record, geologic strata and dental analysis.

Adult↗
PubMed1997

Safety of autologous, ex vivo-expanded human immunodeficiency virus (HIV)-specific cytotoxic T-lymphocyte infusion in HIV-infected patients.

We infused six human immunodeficiency virus (HIV)-seropositive subjects with autologous CD8+ cytotoxic T cells (CTLs) enriched for HIV-specific cytotoxicity targeted against a diversity of HIV epitopes in gp120, gag p17 and p24, and nef. There was no toxicity and no subject deteriorated clinically. In the first 2 weeks, CD4 counts increased for all subjects and plasma viremia decreased in five of six subjects. Twenty-four weeks later, the mean values of all measures of viral burden and surrogate markers of HIV infection were either unchanged or improved, but none of the changes was statistically significant. Two subjects continued to have decreased cell-associated viral burden and another subject had more than doubled CD4 cell count. HIV-specific CTL activity increased in most subjects. The increase in CD4 T-cell counts in the first weeks after the infusion suggests that antiviral CTLs of diverse specificities do not play a significant role in CD4 T-cell decline. The lack of any acute toxicity or adverse effect on viral burden suggests that therapy with antiviral CTLs deserves further study.

Amino Acid Sequence↗
PubMed1997

Recombinant human granzyme A binds to two putative HLA-associated proteins and cleaves one of them.

The release of cytotoxic granule contents by cytotoxic T lymphocytes triggers apoptotic target cell death. Cytotoxic granules contain a pore-forming protein, perforin, and a group of serine proteases called granzymes. We expressed human granzyme A in bacteria as a proenzyme capable of in vitro activation by enterokinase. The recombinant activated enzyme has catalytic activity against substrates with Arg, preferably, or Lys at the P1 position, comparable to trypsin. An enzymatically inactive recombinant granzyme A, with the active site Ser mutated to Ala, was produced and used with affinity chromatography to identify potential substrates. Two granzyme A-binding cytoplasmic proteins of molecular mass 33 and 44 kDa were isolated and identified by tryptic fragment sequencing as PHAP I and II, ubiquitous putative HLA-associated proteins, previously coisolated by binding to an HLA class II peptide. PHAP II forms an SDS-stable complex with recombinant mutant granzyme A and coprecipitates with it from cytoplasmic extracts. PHAP II, either purified or in cell lysates, is cleaved by the recombinant enzyme at nanomolar concentrations to a 25-kDa fragment. PHAP II begins to be degraded within minutes of initiation of cytotoxic T lymphocyte attack. PHAP I and II are candidate participants in the granzyme A pathway of cell-mediated cytotoxicity.

Animals↗
PubMed1997

Tumor necrosis factor constellation polymorphism and clozapine-induced agranulocytosis in two different ethnic groups.

Genes of the major histocompatibility complex (MHC) are associated with susceptibility to different immune and nonimmune mediated diseases. We had reported that the drug adverse reaction, clozapine-induced agranulocytosis (CA), is associated with different HLA types and HSP70 variants in Ashkenazi Jewish and non-Jewish patients, suggesting that a gene within the MHC region is associated with CA. This study was designed to find common genetic markers for this disorder in both ethnic groups. The tumor necrosis factor (TNF) microsatellites d3 and b4 were found in higher frequencies in both Jewish and non-Jewish patients: 51 of 66 (77%) and 48 of 66 (57%), respectively. Comparisons of these frequencies with those of controls, 28 of 66 (42%) and 18 of 66 (27%), were statistically significant (corrected P value = .001 for the d3 allele and .0005 for the b4 allele). On the other hand, the TNF microsatellite b5 was underrepresented in the group of patients, 9 of 66 (14%), when compared with the control subjects, 43 of 66 (65%) (corrected P value = .0005), probably related to protection from CA. Our results show a strong association of some genetic variants of the TNF loci with susceptibility to CA in two different ethnic groups suggesting involvement of TNF and/or associated gene(s) products in the pathogenesis of this hematologic-drug adverse reaction.

Agranulocytosis↗
PubMed1997

Recognition of a small number of diverse epitopes dominates the cytotoxic T lymphocytes response to HIV type 1 in an infected individual.

Mitogen-activated T cell lines may be reproducibly used to identify relatively conserved HIV-1 epitopes that dominate CTL recognition of HIV-infected cells. Using a combination of nested truncations of HIV-vaccinia recombinants encoding HIV-1LAI Env and overlapping peptides that span the coding regions of the HIV-1 SF2 subclone of env, gag, nef, rev, and tat, we have mapped the immunodominant, relatively conserved CTL epitopes recognized by 25 HIV-seropositive individuals with CD4 counts between 100 and 500/mm3 and no history of AIDS opportunistic infection. We could characterize at least 1 peptide CTL epitope recognized by the T cell lines of 18 of 25 of the subjects; the T cell lines from 2 additional subjects recognized HIV-vaccinia presenting targets, but no dominant peptide epitope was identified. CTL epitopes were most frequently encoded by gag (recognized by 16 of 25 patient T cell lines), followed by nef and env (11 of 25 each), and the RT region of pol (9 of 25). Tat and Rev were rarely the sites of CTL epitopes. The identified epitopes occurred predominantly in relatively conserved regions of HIV-1. The mean number of HIV peptides identified at a single time for each cell line was 2.7 +/- 1.7. Although no single peptide dominated CTL recognition in more than four individuals, clusters of epitopes were found in the N-terminal region of gp160 and in two central regions of Nef. The dominant HIV-1 CTL epitopes in infected patients were not predictable on the basis of MHC expression and varied widely in an MHC-diverse population.

Amino Acid Sequence↗